Effects of flexible joints on the 3-D nonlinear coupled responses of a long vertical pipe

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:237936

Cheng, B R; Zheng, Z C ^[1]; Chung, J S ^[2]

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1. Tsinghua Univ., Beijing (China). Dept. of Engineering Mechanics
2. Colorado School of Mines, Golden, CO (United States). Dept. of Engineering

For safe operations in deep ocean, changes in the vibration characteristics of a long pipe or riser are desirable in order to make the vibration of a pipe system controllable, thus increasing its fatigue life. The pipe vibration is often excited by the ship motions, wave forces, and vortex-shedding. Elastic joints along the pipe are presented in an attempt to move the resonance frequencies away from the pipe system. The numerical examples focus on the investigation of single and multiple flexible joints along a long pipe and their effect on three-dimensional (3-D) nonlinear coupled pipe responses, including torsional coupling. The multi-substructure technique is introduced in order to get the governing equation of the entire pipe system. The pipe is subjected to a vertically-varying current flow in establishing the static equilibrium configuration. Dynamic responses are excited by large-amplitude horizontal as well as vertical ship or pipe-top motion. The bending stiffness can affect the bending moments along the pipe and the associated maximum values, but has little influence on the bending deflection. However, the axial stiffness of the joint can greatly change the axial fundamental frequency, as well as static axial displacement, while it has little effect on the static internal axial force. The appropriate position of joints can have a greater influence on the static responses. The dynamic responses to the external excitation of a pipe with multiple flexible joints can greatly be reduced.

• OSTI ID: 237936
• Report Number(s): CONF-950604--; ISBN 1-880653-18-4
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
CONTROL
MARINE RISERS
MECHANICAL VIBRATIONS
OFFSHORE PLATFORMS
PIPELINES
RESPONSE FUNCTIONS